The present invention relates to a fluidized bed, more specifically, a liquid-solids circulating fluidized bed arrangement specially suited for ion exchange processes.
Fluidized beds have been used for a number of different applications such as a gas-liquid, gas-liquid-solid contactors and to carry out a variety of different processes such as chemical reactions.
Fluidized beds have found application in ion exchange process. For example Chase, H. A., xe2x80x9cPurification of Proteins by Adsorption Chromatography in Expended Bedsxe2x80x9d, TIBTECH 12, 296-303 (1994) describes a batch ion exchange process using a conventional fluidized bed for recovering proteins from whole fermentation broth with the presence of bacterial cells. It eliminates the difficult solids separation step and recovers the desired products directly from unclarified whole broth. This process is a batch process employing a conventional fluidized bed.
Burns, M. A. and D. J. Graves, xe2x80x9cContinuous Affinity Chromatography Using a Magnetically Stabilized Fluidized Bedxe2x80x9d, Biotechnology Progress 1, 95-103 (1995) suggested a two-column magnetically stabilized fluidized bed system for the continuous chromatography of biochemical products. The magnetically stabilized fluidized bed system is considered to be complicated and costly.
Gordon, N. F., H. Tsujimura and C. L. Cooney, xe2x80x9cOptimization and Simulation of Continuous Affinity Recycle Extractionxe2x80x9d, Bioseparation 1, 9-12 (1990) describes a process using mixed reactors as opposed to fluidized bed and reported the continuous affinity recycle extraction of proteins using well-mixed reactors. This system, although simple and easy to control, has the disadvantage of a stirred tank systemxe2x80x94the ion exchange efficiency is low and large processing volumes are essential for even a moderate throughput requirement
Porter and Robert, U.S. Pat. No. 3,879,287, xe2x80x9cContinuous ion exchange process and apparatusxe2x80x9d (1975) relates to an apparatus for continuous ion exchange. However, the process described is a semi-continuous process as the recommended eluting means is a batch wise conventional fixed bed ion exchange process.
Himsley and Alexander, U.S. Pat. No. 4,279,755: Continuous countercurrent ion exchange process (1993) teaches a continuous countercurrent ion exchange process for absorbing ions of interest onto ion exchange particles from a feed liquor containing ions which when absorbed on the particles cause the density of the particles to increase. The process comprises the steps of (1) flowing the feed liquor upwardly through a main bed of ion exchange resin particles contained in a main chamber of an absorption column and thereby maintaining the bed in fluidized state; (2) continuously collecting the denser loaded particles from the lower region of the absorption column; (3) passing an outflow of the feed liquor from the upper region of the main chamber upwardly into the lower region of the polishing chamber containing a secondary bed of fluidized ion exchange resin particles whereby residual ions of interest are polished from the liquor, and (4) producing a barren liquor flowing out of the upper region of the polishing chamber. Again, this is a semi-continuous process as the stripping and the regeneration of the loaded ion exchange particles cannot be performed in this device.
It is an object of the present invention to provide a circulating fluidized bed system for liquid solids contact and interaction, more specifically a Liquid-Solids Circulating Fluidized Bed (LSCFB) ion exchanger.
It is also an object of the present invention to provide a process for continuous recovery of the ions of interest for example contaminants in liquid streams or value added products from waste steam using a Liquid-Solids Circulating Fluidized Bed (LSCFB) ion Exchange system.
Broadly the present invention relates to a fluidized bed system comprising a first fluidized bed, means to feed solids into said first fluidized bed adjacent to a first end of said first fluidized bed and means to feed a first fluid into said first fluidized bed adjacent to a second end of said first fluidized bed, said second end being remote from said first end so that said solids and said first fluid flow in counter current, a second fluidized bed, said second fluidized bed being an entraining fluidized bed wherein a means for introducing solids and a means for introducing a second fluid into said second bed are both adjacent to the one end of said second fluidized bed so that said solids and said second fluid introduced into said second bed flow concurrently through said second bed from said one end toward another end of said second fluidized bed remote from said one end, first means connecting said first fluidized bed to said second fluidized bed adjacent to said second end of said first fluidized bed and said one end of said second fluidized bed and said first means connecting including said means to feed solids into said second fluidized bed, and second means connecting said first and said second fluidized beds adjacent said first end of said first bed and said other end of said second fluidized bed, and said second means connecting including said means to feed solids into said first fluidized bed.
Preferably said first and second fluidized beds are substantially vertical columns. Preferably said second means connecting said first and said second fluidized beds includes a separator means for separating solids from fluid and exhausting such separated fluid to provide separated solids.
Preferably second means connecting said first and said second fluidized beds further includes a washer for washing said solids before they are feed into said first end of said first fluidized bed.
Preferably said first means connecting said first and said second fluidized beds includes a second washer washing solids adjacent to said second end of said first fluidized bed before they are introduced into said second fluidized bed.
Preferably said first fluidized bed is an absorber for separating ionic products of interest and said second fluidized bed is a desorber for desorption of ionic products and said solids are ion exchange particles. That is, the said liquid-solid circulating fluidized bed system can preferably be used to recover ionic products of interest by passing ion exchange particles in countercurrent flow with a feed stream of a first fluid through a first fluidized bed for adsorption of ionic products of interest from said feed stream of said first fluid, transferring said particles with adsorbed ionic products of interest from said first fluidized bed to a second fluidized bed and passing said ion exchange particles with absorbed ionic products in countercurrent flow with an extract buffer of a second fluid through said second fluidized bed for desorption of said adsorbed ionic products of interest, separating said second fluid containing said ionic products of interest desorbed from said ion exchange particles by said second fluid to provide regenerated ion exchange particles and returning said regenerated ion exchanged particles into said first fluidized bed to flow in countercurrent with said first fluid.
Preferably said ion exchange particles with absorbed ionic products are washed before being introduced into said second fluidized bed.
Preferably said regenerated ion exchange particles are washed before being returned to said first fluidized bed
Preferably said ionic product is a protein and said first fluid is a fermentation broth.
Preferably said ionic product is a metal and said first fluid is seawater.
Preferably said ionic product is an enzyme and said first fluid is dextrose syrup.